Anti-shrinkage agent for hydraulic material

Abstract

The present invention is related to a shrinkage reducing agent for hydraulic materials which comprises at least one polymer selected from the group consisting of (a) a polymer having a structure derived from the residue of a compound containing 2 to 30 carbon atoms and one active hydrogen atom by the binding thereto of one oxyalkylene chain having a carboxyl-containing side chain, (b) a polymer having a structure derived from the residue of a compound containing 4 to 30 carbon atoms and two active hydrogen atoms by the binding thereto of at least one oxyalkylene chain having a carboxyl-containing side chain, (c) a polymer having a structure derived from the residue of a compound containing 1 to 30 carbon atoms and at least three active hydrogen atoms by the binding thereto of at least one oxyalkylene chain having a carboxyl-containing side chain and (d) a polymer having a structure derived from the residue of an amine by the binding thereto one oxyalkylene chain having a carboxyl-containing side chain.

Description

[0001] The present invention relates to a shrinkage reducing agent for hydraulic materials, a method of producing the same and an additive composition for hydraulic materials.PRIOR ART[0002] Hydraulic materials can give cured products excellent in strength and durability, among others, and therefore are in wide use in the form of cement compositions such as cement pastes, mortar and concrete. They are now indispensable in building civil engineering and architectural structures. Such hydraulic materials, however, have a problem. After curing, the unreacted water remaining in the inside disperses according to ambient temperature, moisture and other conditions and drying shrinkage progresses presumably due to such moisture dissipation to cause cracks to appear in cured products, lowering the strength and durability thereof. Decreases in strength and durability of civil engineering and architectural structures produce serious problems such as endangered safety and increased repairing co...

AI Technical Summary

Benefits of technology

0089] The present invention is further related to an additive composition for hydraulic materials comprising a shrinkage reducing agent for hydraulic materials and a cement dispersing agent, in which additive composition the shrinkage reducing agent for hydraulic materials comprises at least one polymer selected from the group consisting of (A) a polymer having a structure derived from the residue of a compound containing 1 to 30 carbon atoms and one active hydrogen atom by the binding thereto of one oxyalkylene chain having a carboxyl-containing side chain, (B) a polymer having a structure derived from the residue of a compound containing 1 to 30 carbon atoms and two active hydrogen atoms by the binding thereto of at least one oxyalkylene chain having a carboxyl-containing side chain, (C) a polymer having a structure derived from the residue of a compound containing 1 to 30 carbon atoms and at least three active hydrogen atoms by the binding thereto of at least one oxyalkylene chain having a carboxyl-containing side chain and (D) a polymer having a structure derived from the residue of an amine by the binding thereto one oxyalkylene chain having a carboxyl-containing side chain. Such additive composition for hydraulic materials can provide hydraulic materials with good properties contributing to the reduction of drying shrinkage and, at the same time, makes it possible for good dispersibility to be retained even when the amount of water to be added to hydraulic materials is reduced, hence the composition makes it possible to reduce the water content in hydraulic materials to thereby improve the strength and durability of cured products.

0090] The additive composition for hydraulic materials according to the invention may contain another or other ingredients other than the above shrinkage reducing agent for hydraulic materials and a cement dispersing agent. Preferably, however, the composition contains the shrinkage reducing agent for hydraulic materials and the cement dispersing agent.

0091] In the above shrinkage reducing agent for hydraulic materials, the polymer (A) and polymer (B) are the same as the polymer (a) and polymer (b) mentioned hereinabove except that they differ in the range of the number of carbon atoms to be contained in the residue derived from an active hydrogen-containing compound. The polymer (C) and polymer (D) are the same as the polymer (c) and polymer (d) mentioned hereinabove.

0092] The cement dispersing agent is not particularly restricted so long as it is capable of dispersing cement particles. For example, there may be mentioned known cement dispersing agents and water reducing agents as well as ligninsulfonic acid, and polycarboxylic acid type, naphthalene type, melamine type and aminosulfonic acid type water reducing agents. These may be used singly or two or more of them may be used combinedly. The ability of the cement additive to disperse particles in hydraulic materials is improved by incorporating such a cement dispersing agent, the hydraulic materials become excellent in flowability, whereby the workability is markedly improved, and the strength, durability and other characteristics are improved as a result of reduction in water content in the hydraulic materials.

0093] Among the water reducing agents mentioned above, ligninsulfonic acid and the like are generally referred to also as air entraining and water reducing agents while the polycarboxylic acid type, naphthalene type, melamine type, aminosulfonic acid type and like water reducing agents are generally referred to also as air entraining and high-range water reducing agents. Among such water reducing agents, air entraining and high-range water reducing agents are preferably used and polycarboxylic acid type air entraining and high-range water reducing agents can be used with advantage.

0094] The proportions of the above shrinkage reducing agent for hydraulic materials and the cement dispersing agent are not particularly restricted. When an air entraining and high-range water reducing agent is used as the cement dispersing agent, the ratio (shrinkage reducing agent for hydraulic materials / air entraining and high-range water reducing agent) is preferably 1 / 10 to 100 / 1 by weight on the solid matter basis. The addition amount of the shrinkage reducing agent for hydraulic materials is larger than the above weight ratio, the water reducing ability of the air entraining and high-range water reducing agent may be impaired. More preferred is a ratio between 1 / 100 to 50 / 1, still more preferably 1 / 100 to 25 / 1.

Problems solved by technology

Such hydraulic materials, however, have a problem.

After curing, the unreacted water remaining in the inside disperses according to ambient temperature, moisture and other conditions and drying shrinkage progresses presumably due to such moisture dissipation to cause cracks to appear in cured products, lowering the strength and durability thereof.

Decreases in strength and durability of civil engineering and architectural structures produce serious problems such as endangered safety and increased repairing costs.

However, the standard addition amounts of these shrinkage reducing agents are as high as 2 to 6% on the unit cement content basis, so that when used in concrete, they increase the cost of concrete and can never be said to be general purpose agents.

However, this is not easy to synthesize.

However, when the hydrophobicity is excessive, the amount of air in concrete may be reduced to an excessive extent, hence the adjustment of the amount of air may become difficult.

When the hydrophilicity is excessive, an excessive amount of air may be entrained, so that it may possibly become difficult as well to adjust the amount of air to an appropriate level.

When the hydrophobicity of the polymer is excessive, the amount of air in concrete is excessively reduced and accordingly it becomes difficult to control the amount of air.

Conversely, when the hydrophilicity of the polymer is excessive, an excessive amount of air is entrained in the hydraulic material and it becomes difficult to adjust the amount of air to an appropriate level.

When the amount of the ethylenically unsaturated carboxylic acid monomer is less than 0.1% by weight, the resulting polymer will hardly act on cement, possibly resulting in a decrease in shrinkage reducing ability.

When it is in excess of 100 parts by weight, the retardation of curing by the polymer may be enhanced or the reaction mixture will acquire an excessively high viscosity and thus become difficult to handle.

The addition amount of the shrinkage reducing agent for hydraulic materials is larger than the above weight ratio, the water reducing ability of the air entraining and high-range water reducing agent may be impaired.

When it exceeds 10% by weight, hydraulic materials may possibly undergo curing retardation.

When the amount is less than 0.0001% by weight, the shrinkage reducing ability is not sufficiently effected.

When it exceeds 10% by weight, hydraulic materials may possibly undergo curing retardation.

When the amount of water is less than 10% by weight, the respective ingredients are mixed only to an insufficient extent, so that the compositions cannot be molded in some instances or the strength may decrease in other cases.

When it is larger than 80% by weight, the strength of cured products obtained from the cement compositions may possibly decrease.

When it exceeds 60% by weight, higher unit cement content and unit water content are required, possibly giving concrete poor in flowability.

Images